강선경 Seon Gyeong Kang , 이한샘 Han Saem Lee , 임병란 Byung Ran Lim , 이동석 Dong Seok Rhee , 신현상 Hyun Sang Shin

DOI:10.15681/KSWE.2021.37.1.1 Vol.37(No.1) 1-9, 2021

The depletion of dissolved oxygen (DO) in urban streams has a profound effect on the aquatic ecosystem; however, the change in DO by resuspension of sediments and the cause have not been sufficiently investigated. In this study, the physicochemical properties (particle size, and the content of organic and heavy metals) of the sediments of an urban stream (Anyang Stream) and the characteristics of water quality changes (DO, dissolved organic carbon (DOC), dissolved nitrogen (DN), sediment oxygen demand (SOD), and adenosine triphosphate (ATP)) by sediment resuspension were investigated. The sediment content of fine particles (< 0.2 mm) increased from 36.7% to 52.7% from the upstream to the downstream, and the contents of heavy metals and organic matter of the sediment were also higher towards the downstream. The depletion of DO by resuspension was observed in the sediment at the downstream sites (P8, P9), where the fine particle content was high, and biological SOD (BSOD) was more than 88% compared to the total SOD. The increase in BSOD coincided with the increase in ATP. It was also confirmed that the depletion of DO could increase the amount of heavy metals (such as Fe, Mn, and Pb) released from the sediment. Based on the above results, it can be concluded that resuspension of sediments induces rapid water quality changes and may cause accidents, such as fish mortality, during rainfall, and such a water quality effect can be more pronounced in sediments with a high content of fine particles and organic matter and high biological activity.

Dissolved organic matter, Dissolved oxygen, Heavy metal, Resuspension, Sediment oxygen demand

정흥조 Heung Joe Jung , 이재욱 Jae Wook Lee , 곽동희 Dong Heui Kwak

DOI:10.15681/KSWE.2021.37.1.10 Vol.37(No.1) 10-19, 2021

In the flotation process to remove microplastic (MP) particles, the attachment and separation efficiency is determined by the basic physicochemical characteristics of MP particles as well as bubbles. To evaluate the flotation characteristics of MP particles, we carried out a series of simulations using the population balance (PB) model. The initial attachment coefficient (α_o) of MP particles was in the range of 0.2-0.275, and it was slightly lower than that of typical particles, such as clay, debris and algae particles, which exist in water bodies, α_o, 0.3-0.4. The relative bubble number (RBN) attached to the surface of the typical number of bubbles was 0.30 and 0.32 for MP 30 μm and MP 58 μ m, respectively. In comparison, the RBN of larger MP particles (138 μm) was as high as 0.53. Furthermore, smaller microbubbles were required to separate properly or additional treatment needed to be applied to enhance collision and attachment efficiency since the flotation of MP particles was found to be difficult to treat as high-rate. As a result of comparing the removal rate (experimental value) of MP particles obtained from the batch-type flotation apparatus and the flotation removal rate (predicted value) of MP obtained through the PB model, the final particles by the particle size of MP overall except for the initial separation time area. With respect to the removal efficiency, the observed and predicted values were similar, and it was confirmed that the floating separation characteristics and evaluation of the MP particles through the PB model could be possible.

Bubble, Flotation, Microplastics, Particle, Population balance

김호섭 Ho-sub Kim , 김석규 Seok-gyu Kim

DOI:10.15681/KSWE.2021.37.1.20 Vol.37(No.1) 20-31, 2021

In this study, an analysis of the characteristics of organic matter and nitrogenous oxygen demand (NOD) of 17 sewage effluent and wastewater treatments was conducted. High COD_Mn and carbonaceous biological oxygen demand (CBOD) concentrations were observed in the livestock treatment plants (LTP), wastewater treatment plants(WTP), and night soil treatment plants (NTP), but the highest NOD concentration and contribution rates of NOD to BOD₅ were found in sewage treatment plants (STP). There was no significant difference in the CBOD/COD_Mn ratio for each of the six pollution source groups, but the LTPs, WTPs, and NTPs all showed relatively high COD_Mn concentrations in their effluent samples, indicating that they are facilities which discharge large amounts of refractory organic matter. The seasonal change of NOD in all facilities’ effluent was found to be larger than the seasonal change of CBOD, and data results also revealed an elevation of NOD and NH3-N concentration from December to February, when the water temperature was low. There was no significant difference in NH₃-N concentration in relation to pollution source group (p=0.08, one-way ANOVA), but the STP, which had a high NOD contribution rate to BOD₅ of 48%, showed a high correlation between BOD₅ and NOD (r²=0.95, p<0.0001). These results suggest that the effect of NOD on BOD₅ is an important factor to be considered when analyzing STP effluent.

Ammonia nitrogen, BOD_{5, CBOD, CODMn, Nitrogenous oxygen demand, Organic matter}

심규현 Kyuhyun Shim , 김경훈 Gyeonghoon Kim , 임태효 Taehyo Im , 김용석 Youngseok Kim , 김성민 Seongmin Kim

DOI:10.15681/KSWE.2021.37.1.32 Vol.37(No.1) 32-46, 2021

South Korea has been divided into quantities and water quality, and due to a revision of the Government Organization law in June 2018, the controversial water management system was integrated into the Ministry of Environment. The total Maximum Daily Loads System has been called the flower of water quality control, and since 2004, all three major river systems which have been introduced into the Han River system, despite its various difficult environments, and subsequently leading to all of the four major rivers undergoing obligatory implementation since 2013. Currently, the target TMDL (Han River Phase 1 and Other Water Systems Phase 3) for the 2020 stage has been implemented. The domestic TMDL established a basic plan for calculating the load which complies with the unit watershed’s target water quality, as well as an implementation plan for annual load management, both which have been institutionalized in order to evaluate load compliance on a repeated annual basis. Local governments ask external organizations to conduct investigations every year in order to assess the transition, which thereby requires tens of millions of won every year. Therefore, an assessment and management model that can be easily operated at the TMDL personnel level is required. In this study, when the Han river Water System TMDL was implemented in earnest, we confirmed the the water quality improvement effect when TMDL was introduced to major inflow tributaries (TancheonA, JungnangA, AnyangA) under the Seoul City’s jurisdiction through the use of the total amount control unit basin evaluation technique. By presenting customized management measures, we propose the guidelines that are necessary for determining more effective water environmental policies.

Flow duration curve, Load duration curve, Target water quality, TMDL, Watershed evaluation method

최한나 Han Na Choi , 모우종 Woo Jong Mo

DOI:10.15681/KSWE.2021.37.1.47 Vol.37(No.1) 47-54, 2021

Aerobic granular sludge (AGS) can be classified as a type of self-immobilized microbial aggregates measuring more than 0.2 mm. It offers the option to simultaneously remove COD, N, and P that occur in different zones inside a granule. Also, AGS is characterized by high precipitability, treatability with high organic loading, and high tolerance to low temperature. In this study, a sequencing batch reactor inoculated with AGS (AGS-SBR) is a new advanced wastewater treatment process that was proven to grow AGS with integrated nutrient removal and low C/N ratio. A pilot plant, AGS-SBR with a capacity of 225 m³/d was installed at an S sewage treatment plant in Gyeonggi-do. The results of the operation showed that the water quality of the effluent indicated that the value of BOD5 was 1.5 mg/L, CODMn was 11.4 mg/L, SS was 6.2 mg/L, T-N was 13.2 mg/L, and T-P was 0.197 mg/L, and all of these values reliably satisfied an effluent standard (I Area). In winter, the T-N treatment efficiency at a lower temperature of less than 11℃ also showed reliability to meet the effluent standard of the I Area (20 mg/L or less). Analysis of microbial community in AGS showed a higher preponderance of beneficial microorganisms involved in denitrification and phosphorus accumulation compared with activated sludge. The power consumption and sludge disposal cost were reduced by 34.7% and 54.9%, respectively, compared to the domestic SBR type sewage treatment plant with a processing capacity of 1,000 m³/d or less.

Advanced wastewater treatment, Aerobic granular sludge, AGS, Energy saving, Sequencing batch reactor, SBR